Apparatus for the manufacture of abrasive webs



Dec. 21, 1948. N. E. OGLESBY APPARATUS FOR THE MANUFACTURE OF ABRASIVEWEBS Original Filed March 3, 1933 2 Sheets$hee 1.

Dec. 21, 1948, N. OGLESBY 2,456,985

APPARATUS FOR THE MANUFACTURE OF ABRASIVE WEBS Original Filed March 3.1933 2 Sheets-Sheet 2 Patented Dec. 21, 1948 Arman-ms Fox wasMANUFACTURE OF ABBASIVE WEBB Nicholas E. Oglecby, Troy, N. Y., alsignorto Behrg Corporati n. r

tion of Massachusetts Original application March 3, 1933, Serlal No.

N. Y., a corpora- 25, 1943, Serial No. 499,984

659,5.65.- Divided and this application August of the abrasive grain isprimarily eflective,

whereas a grinding wheel is worn, away and successive layers are in turneffective. It. will be appreciated by those skilled in the art thatsurface coated abrasives act by attrition to only a negligible extent,but on the contrary lose their effectiveness because the abrasive;grains finally become dull, or because the spaces between and h aroundthe grains become loaded or filled with disintegration products of thework, or disintegration products of the work in conjunction with theadhesive used to bond the grains to each other and to the backing. Insurface coated abrasives each efiective grain cuts as a miniature tooland microscopic examination of the apparent dust that is removed fromwood, brass, steel and the like shows that the removed particlesresemble shavings or cuttings such as are removed by a plane, or latheor other cutting tool.

From what has been said it will be apparent that it has long been aproblem in the manufacture of coated abrasives to expose upstanding andsharp edges of the grain so that the edges may effectively contact andcut the work. i

In the manufacture of surface coated abrasives it is accepted practiceto first apply anadh'esive coating (known as the making coat) to thebacking, next a coating of grain which is retained, but only lightlyheld by the adhesive, and then after partial drying of the making coat asecond coat of adhesive (known as the sizing coat) is applied. Thissizing coat braces and holds the grain together and also joins with, andmore securely anchors the grains to the making coat of adhesive, whichin turn forms the bond with the backing.

Special methods have been developed in the art to make grains standerect in the making coat of adhesive, but, during sizing, as heretoforepracticed, many of these grains are turned over so that in use theirsharp edges are no longer eflectively presented to the work. Thisturning over of many of the grains in the sizing operation has long beenrecognized, but has not been corrected' because prior to the presentinvention calender rolls have been found most satisfactory for applyingthe sizing coat of adhesive. Much v siderable momentum and 20 Claims.(01. 9118) work has been done to improve calender rolls and their methodor use, but, at best, many grains are turned down rolls and a muchduller of this damaging action.

I am aware that in the, past eflorts have been made to overcome thisdifllculty by spraying the sizing coat of adhesive onto the abrasiveretained by the making coat of adhesive. Such methods overcome theturning down of the sharp edges of the abrasive grains but lead to otherequally serious or more serious defects in the product and have nottherefore supplanted the calender method of sizing.

As an example of the defects of spray sizing as attempted in the past wemay take the specific case of a warm solution of animal glue in water,this being the most commonly used adhesive in product results becausethe coated abrasive industry. If relatively large droplets are sprayed,the droplets may have consome tendency to penetrate to the bottom of theabrasive coat, but these droplets do not coalesce into a smooth uniformfilm of adhesive well joined to the bottom coat of adhesive, and -to thegrains, and broken only by the discontinuities caused by the abrasiveparticles. With such large droplets it'has here tofore been impossibleto secure -a smooth uniform adhesive film, free from air pockets, andeffective in holding the grain without using excessive sizing adhesivewhich in turn fills theclearance spaces around the grains, and isconducive to loading and premature loss of efl'ectiveness of thepidduct. When fine droplets of the warm solution' a're sprayed, due tothe relatively large surface area exposed, evaporation of the solvent,and cooling of the solution is relatively rapid,-so-'that ,the solutionin the droplets becomes very viscous or may even jell before strikingthe abrasive coat; With such small droplets it is easier tosecure anapparently uniform coat of the sizing glue,

' but such sizing coats are relatively ineffective.

These fine viscous droplets with case hardened surfaces do not wet oradhere well to the abrasive grains, thus forming a poor bond. Again suchdroplets do not'completely coalesce, do not penetrate to andaround thebottoms of the"grain, and do not join thoroughly with the making coat ofadhesive, but, on the other hand, they prodiite a bond with an excessivenumber. of air-pockets, tend to cover and dull the edgesofthef grain,form apoorfilm; and when-used in siifliiifnt quantity to hold the grainsunder conditions of use, generally produce a product inferior to thatproduced by calender sizing. For this reason by the pressure of thecalender spray sizin as heretofore practiced has not supplanted c endersizing.

I have discovered a novel method of overcoming the difficultiesheretofore encountered in spray sizing, and also a novel means forimproving calender sizing and coating. It is well known that lacquersand the like are applied with what is known as a spray gun in which thelacquer is atomized with compressed air. When an attempt is made tospray-size coated abrasives with an animal glue solution in this type ofgun, water evaporates from the droplets, and the droplets cool and tendto develop case hardened surfaces before striking the grain so that aproduct is produced with the defects hereinbefore described. By usingsteam under pressure as the atomizing medium and/or applying the productin a semienclosed space substantially filled with an atmosphere of ofsteam, I have been able to overcome the serious defects described andproduce a product superior to that heretofore produced by either thecalender or spray sizing method. In some instances, condensation ofsteam has been found to form harmful droplet of water, but thiscondensation may be eliminated, where objectionable, by using steam witha few degrees of superheat (so-called dry steam), and an insulatedsemi-enclosed space containing an atmosphere of steam for sizingapplication,

The steam is effective in bringing about these improvements for severalreasons. The partial pressure of the steam (water) introduced opposesthe vapor pressure of the fine droplets so that evaporation andconcentration of the solution is reduced to any desired extent- Againvthe retarding of the cooling action of evaporation, and the heatintroduced with the steam serve to keep the droplets fluid even at thesurface where a case hardening tendency has heretofore been encountered.

Instead of spray nozzles or Jets, or so-called spray guns, various othertypes of atomizing devices well known in the art, such as high speedrolls, rotary brushes, and high speed discs, may

,be used to atomize and spray the glue solution.-

In each case, however, it has been found impossible to secure theimproved product desired unless the glue is applied in an atmospherecontaining a substantial proportion of steam effective to resistsubstantially the formation of air pockets. I prefer to use steam orother agent which is inert to the adhesive or, in other words, whichdoes not affect the adhesive action. Moreover, I desire an agentmiscible with the adhesive and which is condensible.

Dry heat or heated air does not serve the purpose. unless the heated airhas added thereto water-vapor, which may be most conveniently added inthe form of steam. In a heated atmosphere containing a large percentageof water vapor, rapid evaporation of the water from the dropletsresulting in concentration of the glues, is prevented, and the dropletsare kept warm and fluid and free from case hardening, thus being in theproper condition for ready wetting and bonding of the grain, as well ascoalescence, and the formation of a good film, In this warm moistatmosphere the droplets are able to flow from the tops toward thebottoms of the grain giving good holding power and free cutting grainswith improved clearance around the tops of the grains. Also since thisoperation is carried out at'or near atmospheric pressure the presence ofa'large percentage of water vapor reduces the percentage oi. permanentgases in the atmosphere surrounding the sizing operation to a verymaterial extent. Under proper conditions the permanent gasmay be almostentirely eliminated. In this way such vapor bubbles and inclusions ascannot be avoided when using the spraying method are very largelyeliminated soon after their formation, and while the glue is still fluidand free to coalesce. That this is true will be readily understood whenwe consider that the spray sized material passes continuously throughand out of the warm vapor laden atmosphere surrounding the sizingoperation and into a cooler and dryer atmosphere. The temperature fallsbelow the dew-point of the water vapor forming the bubbles and othervapor-inclusions, and the vapor condenses to form a relatively smallamount of warm liquid water which is readily miscibl with the gluesolution with the result that the original bubbles and vapor inclusionscollapse under the influence of the external atmospheric pressure. Inthis way the steam aids very materially in eliminatingv air cells orpockets in the adhesive film. It will also be appreciated that the warmdamp atmosphere retains the fluid condition I the glue for a shortinterval of time after the glue is sprayed onto the abrasive coat. Thisincrease of fluidity, and of the time that the glue remains free toflow, allows the glue to level out and eliminate those minor defects andinequalities of glue application, from 1 small spot to small spot, whichcannot be entirely eliminated with mechanical sprays due to thedifficulty of securing and maintaining mechanical perfection in such adelicate operation.

The use of warm solvent vapor to maintain a high degree of fluidity andto accomplish ready penetration and bonding of the grains makes possibleanother unexpected improvement in the art of bonding abrasive grains.Prior to adding the sizing coat it is common practice to allow themaking coat of adhesive to set and to become reasonably well dried, butwhen the sizing coat is added in some cases the water (or other solvent)in the sizing adhesive so softens the bottom adhesive that some of thegrains fall over instead of retaining their upright positions.

With the use of my invention it is possible'to obtain more readypenetration and bonding of the abrasive grains, and this is accomplishedbefore the solvent in the sizing adhesive has time to thoroughlypenetrate and soften the making adhesive with the result that artificialcooling may be used to Jail the sizing adhesive intinie to preventgrains turning over due to softening of the making adhesive. Thisartificial cooling may be accomplished with an air blast or by passingimmediately through a commercial refrigerating machine.

In the accompanying drawings, four forms of apparatus arediagrammatically shown, each of which is capable of performing themethod of the present invention. The forms of apparatus disclosed areillustrative only, and it should be distinctly understood that variousother forms may be used without departing from the present invention.

In the drawings:

Figure 1 is a vertical sectional view of one forms'of apparatus. j

Figure 2 is a vertical sectional view of'asecond form. of apparatus,employing a centrifugal roll.

Figure 3 is a vertical sectional view of another form of apparatus,employing a rotating brush.

Figure 3a is a vertical sectional view of an other form of apparatusemploying calender rolls, and

Figure 4 is a vertical sectional view of an apparatus adapted to applyabrasive particles to a coated backing member in an, atmosphere ofsteam, or the like, which may be used in combination with the otherapparatus disclosed, or

abrasive coat; 3 is a drainage line to carry away any wild drops ofadhesive and any drops formed I by vapor condensation.

'As a specificillustration of. the method of operation we may considerthe sizing with animal glue of 3/0-120 fused aluminum oxide of abrasivequality coated onto a 130# cylinder paper in the conventional way. Acontinuous web of the adhesively coated backing to which abrasive grainshave been appliedis made to travel in front of the spray 4. A solution.of 18%, 114 millipoise hide glue, prepared by soaking the glue in waterand melting in the usual way, and at a temperature of 155 F. is fed inthrough adhesive inlet 2. The rate of flow of adhesive may be controlledby pressure on a closed tank, but is preferably controlled with athrottling valve in line 2 and an excess of liquid head above the valve.The steam at a pressure of 45 lbs. and with suflicient superheat toprevent serious condensation within the enclosed space around the sizingoperation is allowed to flow in through I in an amount controlled by avalve within line I. The amount of steam will vary with the rate atwhich the adhesive is sprayed, and the degrees of superheat will varywith the degree of insulation. of walls -1,the tightness of theenclosure, and external temperatures The adhesive is broken up andthrown against grains as shown in Figure 1.

One atomizer 3 has been shown for simplicity,

but'it will be obvious'to those skilled in the art that a battery ofatomizers may be used and that the atomizers may,- if desired, bemounted on oscillating or traversing carriages. The exact arrangementwill vary with the size of the abrasive grains, the weightof abrasiveadded per unit of area, the amount of adhesive that it is desired to'add per unit area, the width of the coated web and the speed at which.the web is passed before the spray. Operating speeds in the coatedabrasive industry very commonly fall between 100 and 250 linear feet perminute,

and widths of backing very commonly fall between 24 inches and 48,inches. When the sizing operation is completed, the web 5 passes toracks on which it is dried in the conventional Figure 2 shows anotherform of apparatus for carrying out my invention. Ill represents rollersover which the abrasive coated backing 5 is i made to travel; I l is ahigh speed roll used to spray the adhesive against. abrasively coatedbacking 5; I2. is an insulated enclosure within spraying roll H, and isfed from any suitable tank or reservoir; It represents baiiles fortrapping that part of the spray which is not properly directed towardthe abrasive coat; I1 is a trough to catch the drain of adhesive whichis not .sprayed onto the abrasive coat and this recovered adhesive isreturnedto the main storage reservoir by any suitable means such as apump; 5 is the abrasively coated backing which is moved continuouslypast the spray l3; I8 is a slot through which the glue or other adhesiveis fedfrom feeder I 5 to spraying roll II. The volume of adhesivesolution is regulated by the static head on feeder I5 and by thedistance that the tip of slot I8 is set from roll ll.

As a specific example of a sizing operation, we may consider 2/0-100fused aluminum oxide of abrasive quality coated on a backing of 130#cylinder paper. The abrasively coated backing is led past the spray [3at a uniform speed and is supported by rollers H]. A 22% solution of 86millipoise hide glue prepared in the conventional way and held in areservoir above feeder I 5 is fed into feeder at a temperature of 160 F.and with a head of 36 inches, and flows through slot l8 to spray roll IIwhere the greater portion is sprayed so as to strike the abrasivecoating 5. Such adhesive as is not sprayed to the backing is caughtbytrough I! for return to the main reservoir. Prior to, and during thetime that the adhesive is being sprayed onto the 'abmaine coat,superheated steam, at about atmospheric pressure and with about 20 F.superheat, i. e., at a temperature of about 232 F. is fed in at steaminlets I4, and gradually escapes around the cracks in the inclosurethrough which the coated abrasive passes. When the abrasive has passedbeyond the steam chamber it is delivered to drying racks and dried inthe conventional way.

In the apparatus disclosed in. Figure 3, a rotating brush 30 issubstituted for the centrifugal roll disclosed in Figure 2. A casing 3|similar to the casings previously described is provided, and steam isadmitted to the interior thereof through the condult32. A'roll 33 ispositioned to dip into a body of adhesive 34 contained in an appropriatereceptacle, and convey a film of the adhesive upwardly. A doctor blade35 limits the thickness of this film. The rotating brush 30 is disposedin. contact with the periphery of the roll 33 and, when rotated rapidly,functions ,3 to spatter or spray adhesive droplets onto the steam(preferably dry steam) the air inclusions can be almost entirelyeliminated, and that the glue can be made to sink deeper around thebottoms of the grains, thus giving more clearance around the grains, andleaving the-edges of the grains more free to cut.

. Figure 3a shows a chamber 53 having therein a glue container 54 andcalender rolls 55, 58, the

lower roll 55 dipping into the glue and depositing a sizing coat uponthe web 51. The web is passed through the chamber, being directedthereinto by a guide roll '58, and being directed therefrom upwardly bya guide roll 53. The web serves to close oil the bottom of the chamberCommercial abrasive grains are rough and con-' tain depressions andsimilar irregularities.

- when the grains are allowed to fall through air,

or are propelled through air to the adhesively coated backing a certainamount of air is trapped by these irregularities in the grain. It isobvious that there can be no adhesive bond where the mineral surface isseparated from the adhesive surface by entrapped air. I have found thatthese air pockets which separate the glutinous adhesive from a part ofthe abrasive grain surface can be very largely eliminated by allowingthe grains to strike the adhesive in an atmosphere of steam (preferablydry steam). Thus, while supplying the grains, 1 subject them to an agentwhich is condensible and which serves to resist effectively theformation of air pockets.

In this way a more effective bonding of the grains to the adhesive isobtained, since when steam is trapped, it condenses shortly thereafter,creating a vacuum efiect which pulls the still fluid or plastic adhesiveup against the mineral surface from which the adhesive would bepermanently separated by a non-condensible gas-like air.

Referring to Figure 4, an apparatus is disclosed, which is adapted toapply abrasive particles to an adhesively coated backing member, orsheet, in an atmosphere charged with the vapor of a solvent for theadhesive coating. A, backing sheet 40 is provided with a coating ofadhesive on its upper surface by any appropriate means ahead of thesupporting rolls ll, such as the calender rolls 60, the lower one ofwhich dips into suitable adhesive, such as animal glue within acontainer 6|.

The coated sheet travels over rolls ll, 42, 43, into and through anenclosing casing 44. Abrasive particles are contained in a hopper .45and are fed by roll 46 past the adjustable gate 41 to a baiiie plate 48,and thence are deposited upon the adhesively coated backing sheet. Acon-- tinuously and uniformly flowing shower of abrasive particles isindicated at 49.

Steam, or the vapor of any other solvent for the adhesive, is admittedto the casing through conduits 50 and serves as a suitable agenteffective to resist the formation of air pockets in the manner abovedescribed. Any vapor which condenses to liquid form on the walls of theeasing is caught by troughs BI and discharged through conduits 52.Usually, the abrasive coated backing sheet travels to appropriate dryingracks not shown, after it passes over the roll 43. Drying racks areconventional in the art, and are shown, for example, in Figure 1 of thepatent to Oglesby, No. 2,375,813, granted May 15, 1945. In some cases,however, it will be satisfactory to carry the sheet directly from theapparatus-of Figure 4 to any one of the forms of apparatus disclosed inFigures 1 to 3, or to an equivalent sizing coat applying machine. Sincedrying racks which have long been conventional in the art permitcontinuous travel of a web from a making machine to a sizing machine,there will be continuous movement, whether or not drying racks are used,from the making-coat chamber of Figure 4 to one of the various forms ofsizing coat chambers shown in Figures 1, 2, 3 and 3a.

The apparatus of Figure 4, which applies abrasive grains to anadhesively coated backing sheet, in an atmosphere of a vaporizedsolvent, cooperates with the forms of apparatus disclosed in. Figures 1to 3, which applies an adhesive coating to the abrasives in anotheratmosphere charged with a vaporized solvent, because the novel stepperformed by each apparatus contributes to a superior final product,characterized by the entire absence of air bubbles, pockets, or thelike.

In i'ie examples heretofore cited reference has been almost entirely toglues as typical of adhesives that are soluble in, and are used in watersolution. These examples have been treated very fully since glue is theadhesive most commonly used inthe coated abrasive industry. My inventionis not, however, limited to use with glues or to adhesives that aresoluble in water. Solutions of varnishes, of natural resins and ofsynthetic resins in volatile organic solvents also find application inthe coated abrasive industry. As examples of common solvents used withvarnishes we may cite oleum spirits and highflash naphtha. With certainsynthetic and natural resins these same solvents may be used but suchvolatile organic solvents as alcohol and acetone are also used.

As specific examples I may cite solutions of ester gum varnishes inoleum spirits, solutions of oil modified alkyd resins (often calledvarnishes) in high-flash naphtha, solutions of shellac in alcohol, andsolutions of phenolformaldehyde resins in alcohol or acetone. Thevarnishes and synthetic resins usually are most advantageously set orcured by using heat after application of the sand-and the adhesivecoats. Solutions of adhesives of the varnish and resin type as a ruletend to set to a very viscous or to a jelly like mass less readily thananimal glues and do not as a class give so much trouble due to casehardening and increase in viscosity of the droplets during the spraysizing operation. Such adhesives do, however, trap air and give rise toair pockets and bubbles in the final film, especially when the spraysizing system is used. My invention very materially reduces these airinclusions in adhesives of these types and also causes inequalities inthe sprayed adhesive to flow out and give a more uniform and perfectlybonding adhesive coat with proper clearance between the rains.

When volatile organic solvents are used instead of water to dissolve theadhesive in question I introduce around the sizing operation warm or hotvapor of the particular organic solvent in question instead of. steam.The vapor temperature should preferably be held above the dew point soas to prevent condensation of droplets on the goods in process or on theequipment so that they subsequently drain onto the goods. The vaporintroduced slows down the, rate of evaporation of the solvent from thedroplets, prevents surface concentration in the droplets, and, to theextent present, replaces the permanent gas (air). With sufficient vaporpresent the same will serve as an agent effective to resist theformation of air pockets. The permanent gases (air) can be almostentirely eliminated so that any bubbles or gas inclusions formed in theadhesive film consist of condensible vapor, which vapor shortlythereafter readily condenses to form minute parto give a union betweenadhesive to or 'csive to grain.

Th in the practice of my invention I use an agent which is a solvent forthe adhesive and inert thereto in the sense that it does not affect theadhesive action. For example, an atmosphere comprising a substantialproportion of water vapor is used where water is the solvent, of alcoholvapor where alcohol is the solvent, of high flash naphtha vapor wherehigh flash naphtha is the solvent. In general, I use vapor of the samevolaadhesive tile solvent that is used to dissolve the adhesive.

whereby the droplets are kept fluid and free from case hardening intheir passage to the abrasive coat, and whereby pockets, bubbles, andother permanent gas inclusions in the adhesive coating are largelyeliminated. When I state that I use an fatmosphere or "atmosphere of anagent," I mean that the surrounding or influencing conditions are ofsuch character as to accomplish the result desired, and do not intend torestrict myself to any preciseatmospheric condi- .tionsince theproportion 01' the charge of any agent in the atmosphere will dependupon par- .ticular conditions and the precise results desired.

carrying out the sizing operation in an atmos-' phere charged with warmalcohol vapor, or warm acetone vapor will eliminate air pockets, andother air inclusions so as to produce superior bonding and free cuttingabrasive grains.

i As is well known mixed solvents are sometimes used to dissolveadhesives. As examples we may cite solutions of nitrocellulose ina-mixture of alcohol and ether, or in a mixture of amyl acetate andbutyl alcohol; solutions of common varnishes in. a mixture of turpentineand oleum spirits, or

of other varnishes in a mixture of oleum spirits and high-flash naphtha.In such cases it will mixture of the solvent vapors.

This invention has been .illustrated with particular reference to itsuse in making sinele abrasive coats. It is obvious that the inventionmay be used to build up any thickness of abrasive coat desired by arepetition of the process. Thus, after the initial coating of abrasiveis made, the sizing operation may becarried out as disclosed, a secondcoat of abrasive may be applied, then a second sizing operation may becarried out. and the cycle may be-repeated until the thickness requiredis obtained.

This application is a division of application Serial No. 659.565. flledMarch 3. 1933. which was issued as Patent 2,403,018, dated July 2, 1946.

I claim:

1. Apparatus for the manufacture of granular coated webs comprisingmeans for applying liquid adhesive to a web. means whereby the partial pessure of a solvent in the atmosphere in a chamber may be controlled toprevent drying, rain applying means for applying granular part cles tosaid adhesive coated web, and means for passing sa d adhesive coated webthrough saidchamber and past said grain applying means ing said granularmaterial.

2. Apparatus for the manufacture of granular coated webs comprisingmeans for applying liquid adhesive to a web. a chamber through whichsaid adhesively coated web is passed, means whereby the atmosphere insaid chamber may be controlled to prevent drying of said liquid adhesiveand means for applying granular particles to the adhesively coated webwhile the adhesive is in a condition to wet and pick up the abrasivegrains.

3. Apparatus for the manufacture of granular coated webs comprising achamber for receiving a web, means for creating partial pressure of asolvent in the atmosphere of the chamber to prevent drying, means forpassing an adhesive coated web through said chamber, and means forapplying granular particles to said adhesive coated web whereby thegranular material is applied to the web while the adhesive is incondition for receiving said granular material.

4. Apparatus for the manufacture of granular coated webs comprising achamber for receiving an adhesively coated web. means for maintainingtemperature and humidity condition of the atmosphere in the chamber toprevent drying of adhesive on an adhesively. coated web passed throughthe chamber, means for passing an adhesive coated web through saidchamber. and means for supplying granular particles to the adhesivecoated surface of the web while the adhesive is in condition forreceiving said granular particles.

5. Apparatus for the manufacture of granular coated webs comprisingmeans for applying liquid adhesive to a web, means whereby theatmosphere adjacent said web may be controlled to prevent drying of thesaid liquid adhesive and means for applying granular material to saidadhesively coated .web prior to substantial drying of said adhesive.

6. An apparatus for applying a sizing coat to an closed casing, gasinlet means for said casing whereby a heated vapor of a solvent-for thesizing adhesive may be added thereto and a heated,

solvent charged atmosphere created therein,

means for conveying an abrasive article into said casing and forpreventing the substantial escape 01'. said gasified solvent from saidcasing, and means in said casing for applying an adhesive sizing coat tosaid article while in said heated solvent-charged atmosphere.

7. An apparatus for applying 'a sizing coat to a flexible abrasivesheet, comprising a substantially enclosed casing, gas inlet means forsaid casing, whereby a heated vapor of a solvent for the sizing adhesivemay be added thereto and a heated, solvent-charged atmosphere createdtherein, means for conveying said flexible abrasive sheet into andthrough said casing and for preventing the substantial escape of saidgasified .in said heated solvent-charged atmosphere.

8. An apparatus for applyin a sizing coat to I a flexible abrasivesheet, comprising a substantially enclosed casing, gas inlet means forsaid solvent from said casing, and spray means in said casing forapplying an adhesive sizing coat to said sheet while in said heatedsolvent-charged atmosphere.

9. An apparatus for applying a sizing coat to a, flexible abrasivesheet, comprising a substantially enclosed, insulated casing, a steampipe communicating with the interior of said casing, whereby anatmosphere charged with steam may be created therein, means forconveying said flexible abrasive sheet into and through said casing andfor preventing .the substantial escape of said steam from said casing.and means in said casing for applying a water soluble adhesive sizingcoatto said sheet while in said atmosphere charged with steam.

10. An apparatus for the adhesive anchoring of abrasive grains to acarrier backing by means of abrasive grain holding making and sizingadhesive layers in the manufacture of coated abrasives comprising achamber, inlet means for said chamber, whereby an atmosphere of agasifled solvent for the adhesive may be created therein, means forconveying the carrier backing through said chamber, and means in saidchamber for bringing about contact between said abrasive grains and saidadhesive whereby the said abrasive grains and the said adhesive areexposed to said atmosphere .before contact therebetween, and whereby astrong adhesive union, free from air bubbles and pockets, is attainedbetween the grains and the adhesive and the abrasive grains are flrmlyanchored to the backing.

11. An apparatus for the application of a sizing coat of adhesive overthe abrasive grains anchored to a flexible backing by 9. making coat ofadhesive in the manufacture of coated abrasives comprising a confiningspace, inlets for said confining space whereby an atmosphere of agasifled solvent for the sizing adhesive may be created therein, meansfor conveying the said web with the said abrasive grains anchoredthereon through the said confining space and means for applying the saidsizing adhesive over the said abrasive grains in the solvent atmosphereof the said confining space whereby the sizing coat is applied in anatmosphere in which the greater part of the air has been replaced withcondensible solvent vapor and substantially all air inclusions andpockets are eliminated from the union between the grains and the sizingadhesive and from the union between the sizing and making adhesives.

12. An apparatus for the anchoring of abrasive grains on a flexiblereinforcing backing by means of an adhesive coating applied to the saidbacking, comprising means for applying a coating of an adhesive inliquid form to said backing, a chamber, inlets for said chamber wherebyan atmosphere of a gasified solvent for the said adhesive may be createdtherein, means for conveying the said adhesive coated web through thesaid chamber and means for applying abrasive grains to the adhesivecoating on the flexible backing in the solvent atmosphere of the saidchamber whereby both the grains and the adhesive on the coatedbackingare contacted by the solvent atmosphere before contact betweenthe said abrasive grains and the said adhesive and whereby the abrasivegrains are applied to the adhesive in an atmosphere in which the greaterpart of the air has been replaced by condensible solvent vapor andsubstantially all air inclusions and pockets are eliminated from theunion between the said abrasive grains and the said adhesive coating.

13. An apparatus for the application of a sizing adhesive in themanufacture of coated abrasives comprising a chamber, inlets for saidchamber whereby an atmosphere of a gasiiied solvent for the sizingadhesive may be created therein, means for conveying the said web withthe said abrasive grains anchored thereon through the said chamber andcalender means for applying the said sizing adhesive over the saidabrasive grains in the solvent atmosphere of the said chamber wherebythe sizing coat is applied in.an atmospherein which the greater part ofthe air has been replaced with condensible solvent vapor andsubstantially all air inclusions and pockets are eliminated from theunion between the grains and the sizing adhesive and from the unionbetween the sizing and making adhesives.

14 Apparatus for the manufacture of granular coated webs comprisingmeans for applying liquid adhesive to a web, a chamber, means for addingthe vapor of a solvent for the adhesive to the atmosphere within thechamber, grain applying means for applying granular particles to saidadhesive coated web and means for passing said adhesive coated webthrough said chamber and past said grain applying means whereby thegranular material is applied to the web while the adhesive is incondition for receiving said granular material, a further chamber, meansfor adding the vapor of asolvent for a sizing adhesive to the atmospherewithin the said further chamber, means for applying a liquid sizingadhesive over said granular particles previously applied to saidadhesive coated web within said further chamber, and means forcontinuously passing said granular coated web into and through saidfurther chamber from said first-mentioned chamber. v

15. Apparatus for the manufacture of granular coated webs comprisingmeans for applying liquid adhesive to a web, means whereby the partialpressure of a solvent in the atmosphere in a chamber may be controlledto prevent drying, grain applying means for applying granular particlesto said adhesive coated web, means for passing said adhesive coated webthrough said chamber and past said grain applying means whereby thegranular material is applied to the web while the adhesive is incondition for receiving said granular material, means whereby thepartial pressure of a sizing coat solvent in the atmosphere in a chamberfor applying a sizing coat may be controlled to prevent drying, meansfor adding the vapor of a solvent for a sizing adhesive to theatmosphere within said chamber, means for applying a liquid sizingadhesive over said granular particles previously applied to saidadhesive coated web within said first mentioned chamber, and means forcontinuously passing said granular coated web into and through saidsecond chamber from said first-mentioned chamber.

16. Apparatus for the manufacture of granular coated webs comprisingmeans for applying liquid adhesive to a web, a chamber having meanswhereby the partial pressure of a solvent in the atmosphere in thechamber may be controlled to prevent drying, grain applying means forapplying granular particles to said adhesive coated web, means forpassing said adhesive coated web through said chamber and past saidgrain applying means whereby the granular material is applied to the webwhile the adhesive is in condition for receiving said granular material,a second chamber for the application of a coat of sizing means forapplying sizing material to the granular surface of the web while it isin said second chamber, means for supplying to the second chamber andmaintaining in the zone of application of the sizing material anatmosphere charged with a solvent for said material, and means forfeeding and directing the web continuously from the first-mentionedchamber into and through said second chamber. I

.17. Apparatus for the manufacture of granular coated webs comprisingmeans for applying liquid adhesive to a web, a'chamber through whichsaid adhesively coated web is passed, means whereby vthe atmosphere insaid chamber may be controlled to prevent drying of said liquidadhesive, means for applying granular particles to the adhesively coatedweb while the adhesive is in a condition to wet and pick up the abrasivegrains, a second chamber for the application of a coat of sizingmaterial to the granular surface of the vent drying, means for passingan adhesive coated I web through said chamber, means, for applyinggranular particles to said adhesive coated web whereby the granularmaterial is applied to the web while the adhesive is in condition forreceiving said granular material, a second chamber for the applicationof a coat of sizing material to the granular surface of the web, meansfor applying sizin material to the granular surface of the web while itis in said second chamber, means for supplying to the second chamber andmaintaining in the zone of application of the sizing material anatmosphere charged with a solvent for said material, and means forfeeding and directing the web continuously from the firstmentionedchamber into and through said second chamber.

19. Apparatus for the manufacture of granular coated webs comprising achamber for receiving an adhesively coated web, means tor maintainingtemperature and humidity condition of the atmosphere in the chamber toprevent drying of adhesive on an adhesively coated web passed' throughthe chamber, 'means for passing an adhesive coated web through saidchamber, means for supplying granular particles to the adhesive coatedsurface of the web while the adhesive is in condition for receiving saidgranular particles, a second chamber for the application of a coat ofsizing material to the granular surface of the web, means for applyingsizing material to the granular surface of the web while it is in saidsecond chamber, means for supplying to the second chamberand maintainingin the zone of application of the sizing material anv atmospherechargedwith a solvent for said material, and means for feeding anddirecting the web continuously from the first-mentioned chamber into andthrough said second chamber.

20. Apparatus for the manufacture of granular coated webs comprisingmeans for applying liquid ular material and while it is travelling acoat of terial.

sizing material, and means for maintaining in the zone of application ofthe sizing material an atmosphere charged with a solvent for said ma-NICHOLAS E. oGLEsBY.

REFERENCES CITED The following references are'oi record in the file ofthis patent:

UNITED STATES PATENTS (1 Number Name a Date 157,068 Edwards Nov. 24,1874 349,463 Sparks Sept. 1, 1888 506,389 Calus Oct. 10, 1893 1,595,491Minton Aug. 10, 1928 2,198,766 Gallagher Apr. 30, 1940 2,201,194 Meltonet a1. May 21, 1940 2,281,558 Cross May 5, 1942 2,403,018 Oglesby July2, 1946 FOREIGN'PA'I'ENTB Number -,Country Date 128,658 Great Britain .1July 3, 1910

